The present invention relates to a process for producing a heat pipe comprising a steel container having water enclosed therein as a working liquid.
Heat pipes comprising a steel container having water enclosed therein as a working liquid are in wide use because of the high strength of the container and the superior characteristics of water as the working liquid. However, such heat pipes have the problem that iron reacts with water to evolve hydrogen gas, impairing the performance of the heat pipe in a short period of time. More specifically, the evolved hydrogen gas diffuses through the wall of the steel container in the form of atoms and becomes partly released from the container at a constant rate, but a major portion of the hydrogen gas remains in the condensing portion within the container to lower the performance of the heat pipe. While the steel container is sometimes aluminized over the outer surface to provide protection against corrosion and also to attach thereto aluminum fins having a brazing layer by vacuum brazing, the hydrogen gas diffusing through the container wall is then prevented from escaping from the container by the resulting aluminized coating.
Accordingly, the following means have heretofore been employed to prevent the evolution of hydrogen gas and to preclude deterioration of the heat pipe due to the evolution of hydrogen gas.
(1) Addition of an inhibitor to the working liquid, i.e. water, to inhibit the reaction between water and iron.
(2) Copper plating of the inner surface of the steel container.
(3) Provision of a hydrogen absorbing material within the container.
(4) Provision of a linear hydrogen passing member of Pd or the like for holding the interior of the container in communication with the outside.
These means nevertheless fail to inhibit hydrogen gas and to prevent deterioration of the heat pipe due to the evolved hydrogen gas when the pipe is used for a prolonged priod of time.